Film-Tech Forum ARCHIVE: Subtitle and 4 K

This is topic Subtitle and 4 K in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Frederick Lanoy (Member # 5416) on 04-06-2014, 03:16 PM:

Hello everybody,

We had a issue with a 2 K content on a 4 K projector. I don't really understand what happened.

Barco DP4K32B.
Dolby DSS220 + IMB (so no subtitle engine).
The movie : 2 K. Only some short scenes with subtitles.

Problem was : bottom line of the subtitle was invisible. My colleague had a good idea : he tried to change the setting on the PCF file (Active aera). Now active aera is : 4096 X 900. Problem solved. Good.

Yet, i still don't understand why TI software is not able to put the subtitles correctly on the chips. Have you experienced some similar issues on different brands ? Is there an update that solves this problem ?

Thanks.

Posted by Marco Giustini (Member # 4544) on 04-06-2014, 04:07 PM:

I believe you should have two sets of macros: a 2K set and a 4K set. While a 2K picture will be fine when run with a 4K macro, subtitles won't be properly aligned.
I am not sure of the reason for that, but I know two sets of macros are needed.

In your case, select 2048x858 and your subs will be in the right place.

I reckon the TI board is capable of understanding that a 2K picture is being fed - even though the active area is 4K - but the vertical offset for subtitles is still referring to the active area. May be mistaken though.

Posted by Steve Guttag (Member # 268) on 04-07-2014, 06:40 AM:

That is correct...for subtitles, you HAVE to run the proper PCF file. Subtitles are generated in the ICP and use the subtitle file that defines where the subtitles go by the number of lines from the bottom of the image. So, if the subtitle definition specifies that the subtitles go 10-lines up from the bottom, then that is where it will be. When you run a 2K movie with the 4K PCFs, then what the scaling engine does is see the 2048x1080 image and does a 2x magnification...however the subtitles do not go through the scaling engine, they are generated originals...it will start those subtitles right where the definition says...which will be down below the image based on the 4K PCF.

If you select the 2K PCF so that the active area is properly defined, then the subtitles will be where they should be.

Conversely, if you run 4K movies with the 2K PCF file...your image will be formatted incorrectly as it will take the middle of the image and scale that up to fill the 4K raster.

Posted by Frederick Lanoy (Member # 5416) on 04-14-2014, 08:56 AM:

Thanks Marco and Steve. I understand now.

I guess that this problem does'nt exist with the subtitle engine process ? As the server handle subtitles instead of the TI software ?

And one more question, is there an active aera setting in Christie and NEC's software (PCF file). I don't remember that when i tried to create Channels / Titles.

Posted by Marco Giustini (Member # 4544) on 04-14-2014, 03:15 PM:

It's called source.